Remove some monkey patching in src/sage/__init__.py

[mkoeppe]

To make sage a namespace package, we need to get rid of src/sage/__init__.py.

It currently contains:

• definition of __all__ (no longer needed; has no effect on completion, neither in plain python3 nor IPython)
• definition of __version__ (unused)
• preloading of zlib (introduced in Wrong zlib library might be loaded #23122)
• Move load_ipython_extension from sage.__init__ to sage.repl.__init__ #32489: load_ipython_extension (introduced in Do not import IPython at startup #18726): This function is defined in module sage so that %load_ext sage works (see http://www.slabbe.org/blogue/categorie/ipython/); we forgot to define the corresponding function that would make %unload_ext sage work
• Remove monkey patching of inspect.isfunction in sage.__init__ #32479: monkey patching of inspect.isfunction to support Cython functions (introduced in Add IPython support for Cython functions #25373)
• monkey patching of importlib.machinery.ExtensionFileLoader (introduced in Fix Cython tracebacks on Python 3 #24681); the quest to get an upstream fix merged was apparently abandoned - bpo-32797: linecache should search for sources if loader doesn't find them python/cpython#6653
• monkey patching of sqlite on Cygwin (introduced in Cygwin: system sqlite3 modifies DLL search order #30157)

In this ticket we remove the ones that are not needed any more, and some others to another module init. #32479 and #32489 will take care of the leftovers.

CC: @kiwifb @jhpalmieri @embray

Component: refactoring

Author: Matthias Koeppe

Branch/Commit: af6642f

Reviewer: François Bissey

Issue created by migration from https://trac.sagemath.org/ticket/31420

[mkoeppe]

comment:2

Sage development has entered the release candidate phase for 9.3. Setting a new milestone for this ticket based on a cursory review of ticket status, priority, and last modification date.

[jhpalmieri]

comment:12

It seems that removing __version__ and __all__ is harmless. I don't know about the zlib issue: I tried moving the import to all.py and everything worked, but that's hardly an exhaustive test.

[mkoeppe]

comment:13

We can probably move it (and also the sqlite monkey-patching on cygwin) to a module that is loaded very early such as sage.cpython.__init__.

[mkoeppe]

Branch: u/mkoeppe/meta_ticket__review_remove_monkey_patching_in_src_sage___init___py

[jhpalmieri]

Commit: ad587cf

[jhpalmieri]

comment:15

Do you also want del _sys?

---

New commits:

91ec0f2	src/sage/__init__.py: Remove __all__
949d787	src/sage/__init__.py: Remove __version__
f77a98e	src/sage/__init__.py: Move 'import zlib' to src/sage/cpython/__init__.py
2e9ea56	src/sage/__init__.py: Move monkey-patch of ExtensionFileLoader to src/sage/cpython/__init__.py
ad587cf	src/sage/__init__.py [Cygwin]: Move monkey-patch of sqlite to src/sage/cpython/__init__.py

[sagetrac-git]

Changed commit from ad587cf to af6642f

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

af6642f

src/sage/cpython/__init__.py: Clean up sage.cpython module

[mkoeppe]

Author: Matthias Koeppe

[kiwifb]

comment:19

Where does the del _zlib come from in sage/cpython/__init__.py? It wasn't present in sage/__init__.py and the ticket above that group only talks about import zlib. Is mentioning that ticket obsolete? Is the whole block obsolete when we favor system zlib whenever possible?

[mkoeppe]

comment:20

The del introduced in af6642f just removes the binding of the name _zlib created by the import statement from the sage.cpython module. Likewise the other dels in this commit.

[kiwifb]

comment:21

Call me obtuse, why do you import and then delete straight away? Is it a cleaner way to make sure that the right library is loaded while you may not want it around in this particular unit?

[mkoeppe]

comment:22

The importing there is just to trigger loading some shared library.
One could use a function from importlib instead of using import but that's a tiny bit more obscure

[kiwifb]

comment:23

Thank you for taking the time to answer my questions. It looks good to go.

[kiwifb]

Reviewer: François Bissey

[mkoeppe]

comment:24

Thanks for reviewing!

[vbraun]

Changed branch from u/mkoeppe/meta_ticket__review_remove_monkey_patching_in_src_sage___init___py to af6642f